These will be going on a 4Motion Sportwagen (smaller master cylinder than GTI/PP/R), so pedal travel is a potential concern. Sounds like it's worth returning the 340's.
Are these the 345mm rotors I'm looking for? https://www.fcpeuro.com/products/vw-brake-disc-zimmermann-z-coat-1k0615301m#description
Those are what I bought.